White-Oak Bark - Quercus alba. U. S.

Black-Oak Bark - Quercus tinctoria. U. S.

Quercus. Quercus pedunculata. Br.

The bark of most of the oaks is possessed of properties very nearly identical, so that one species may generally be substituted for another without great disadvantage. Q. Robur and Q. pedunculata, the latter of which is the common British oak, are the species most used in Europe; Q. alba or American white-oak, Q. prinus or white chestnut-oak, Q. montana or rock chestnut-oak, Q.falcata or Spanish oak, and other indigenous species, have been indifferently used in this country. Our Pharmacopoeia has adopted Q. alba or white-oak, as the representative of the oaks in general, being one of the most astringent, and Q. tinctoria or black-oak, as possessing somewhat different properties, and requiring a separate consideration. It is the inner bark, in all the species, which is principally efficacious; and this, therefore, should be employed to the exclusion of the epidermis, when the latter is readily separable. The bark is better from the young branches than the old, and gathered in the spring than at other seasons.

Sensible Properties. The inner bark has a coarse, fibrous texture; a light-brownish or reddish-brown colour; a slight peculiar odour, little perceptible in single pieces, but very obvious in mass; and a rough, astringent, bitterish taste.

Active Principles

These are tannic acid of the kind found in galls, gallic acid, and a bitter crystallizable, neuter substance, called quercin, which has been found in the bark of European oaks, and probably exists in most or all of the species. Of these principles, tannic acid is the most abundant and most important. They are all extracted by water and alcohol.

Incompatible. These are the same essentially as those of galls; but the bark of the British oak is said not to precipitate tartar emetic.

Peculiarities of Q. tinctoria, or Black-oak Bark. This variety is more bitter than most of the others, and differs also in staining the saliva yellow when chewed. Besides the tannic and gallic acids, it contains a peculiar colouring principle, called quercitrin, which renders it valuable as a dye-stuff, in which capacity the coarsely powdered bark is considerably used under the name of quercitron.

Effects on the System

The effects of oak bark are those of a mild astringent and tonic. Experiments performed with it at the veterinary school of Lyons appear to show that, when largely taken, it renders the blood redder, thicker, and more viscid, and at the same time diminishes the putrefactive tendency after death. The blood of a horse, which was made to take twenty pounds of the bark in a month, was said, at the end of that time, to have undergone the change referred to; and the body of the animal, which was killed, remained two months without the least sign of putrefaction.

Black-oak Bark is said to differ from the other varieties in having some tendency to operate on the bowels.

Therapeutic Application

Oak bark has been used internally in chronic diarrhoea and dysentery, in passive hemorrhage from the bowels, and in intermittent fever; but it is little employed in this way. The inhalation of the odorous matter which exhales from large quantities in mass, has been thought to be advantageous in phthisis; because this disease has been observed to prevail less among tanners than with other classes of people; but more accurate and copious statistical details are wanted to establish the fact. The black-oak bark, in consequence of its supposed irritant effects on the bowels, should not be given in cases of diarrhoea.

The topical use of the bark is much greater than the internal. The decoction has been employed as a bath, especially for children, in marasmus, scrofula, chronic diarrhoea, cholera infantum, and intermittent fever. It has also been found useful as a gargle in prolapsus of the uvula and inflammation of the fauces; as an injection in leucorrhoea, prolapsus uteri, prolapsus ani, and dropsical cysts; and as a wash, or in the form of poultice, in piles,, old and obstinate ulcers, edematous swellings of the limbs and joints, and even in the cure of reducible hernias, aided by the use of a truss. The powder made into a cataplasm is said to have been useful in external gangrene; and the infusion taken from tanners' vats has been beneficially employed in old, flabby, and ill-conditioned ulcers.

Administration

The dose is from thirty grains to a drachm. An extract made by boiling the decoction to dryness has been given in half the quantity. The decoction (Decoctum Quercus Albae, U. S.), made in the proportion of an ounce to a pint of water, is given in the dose of two fluidounces. In each instance, the dose may be repeated from three to six times in a day. For external use, the decoction may be made with twice the proportion of bark just mentioned.

The fruit of the oak, or acorn, is more astringent and bitter than the bark, and has been considerably used in scrofulous affections. It is said to be more efficacious when previously roasted, in consequence of a supposed beneficial influence of the resulting empyreumatic products upon the nervous system. The most agreeable form for use is that of an infusion or decoction, prepared from the roasted and ground fruit, exactly in the manner of coffee, and taken like that with sugar and cream.

For an adult, half an ounce of acorns may thus be prepared for each morning and evening meal; for a child, from half a drachm to a drachm, with a convenient quantity of water.

Acorns have been sometimes used as food in periods of famine; but they are said to produce for a time obstinate constipation, followed in the end by diarrhoea and cholera.